Long-range objectives are: (1) to gain improved understanding of the relation of auditory discrimination to children's learning disabilities, the impact of age-related changes in auditory discrimination on communication skills, and ways in which auditory discrimination relates to other child characteristics; (2) to test sufficiently large and representative samples so that outcomes may be broadly generalized to the U.S. population; and (3) to develop a clinical test procedure with a scoring system that efficiently identifies children who are at risk for learning problems associated with poor auditory discrimination (even though they exhibit normal auditory sensitivity on typical audiological test procedures). Immediate goals are to estimate the prevalence of auditory discrimination problems in large samples of normal and learning-disabled children and to track a sample of 200 normal and learning-disabled children over at least a four year period to gain understanding of developmental changes in auditory discrimination. The experimental auditory discrimination task employed in this work is an adaptive psychophysical procedure with trial-by-trial feedback and "catch trials." Pairs of stimuli to be discriminated are selected from two continua of five-formant computer-synthesized syllables in which initial consonants differ in the place-of-articulation and voicing-onset-time features, respectively. Major interest is in the relative performances of different groups of children, who are tested in schools using portable computer-based equipment. All procedures associated with this task have been selected to enhance the likelihood of future clinical usefulness. Data are also collected concerning children's pure tone sensitivity, middle ear impedance, Speech Reception Threshold, word identification (i.e., "speech discrimination"), receptive vocabulary and language, speech production, school class placement, history of school services previously received, and other background information from school records. Results from the first two years, when more than 200 children have been tested in the Prevalence Component, alone, suggest that it will be possible to establish a clinically-useful scoring system for the auditory discrimination task. Intercorrelations among auditory discrimination and other child characteristics raise provocative questions of theoretic and applied interest to psychoacousticians, psycholinguists, clinical audiologists and learning-disability diagnosticians, among others.